1. Field of the Invention
The present invention relates to a film forming method, a semiconductor device and a semiconductor device manufacturing method and, more particularly, a film forming method, a semiconductor device and a semiconductor device manufacturing method for covering wiring with an interlayer insulating film having a low dielectric constant.
2. Description of the Prior Art
In recent years, miniaturization and reduction in thickness of the pattern have been required for a higher degree of integration and higher density of semiconductor integrated circuit devices, as well as for higher speed of data transfer.
Therefore, an insulating film having a low dielectric constant (referred to as a xe2x80x9clow dielectric constant insulating filmxe2x80x9d hereinafter) and small RC delay is employed. Such insulating films include SiOF films having a relative dielectric constant of 3.5 to 3.8, porous SiO2 films having a relative dielectric constant 3.0 to 3.1, etc., for example.
However, such a low dielectric constant insulating film takes up and passes moisture. Therefore, if such a low dielectric constant insulating film is employed alone as the interlayer insulating film, corrosion of the wiring and increase in the leakage current easily result. In order to prevent same, a barrier insulating film containing Si and N or Si and C is often interposed between the wiring and the low dielectric constant insulating film.
More particularly, in a semiconductor device having multi-layered wiring, an interlayer insulating film including barrier layers is formed between the upper wiring and the lower wiring. The interlayer insulating film containing barrier layers is formed by laminating a barrier insulating film containing Si and N or Si and C, a low dielectric constant insulating film, and a barrier insulating film containing Si and N or Si and C, in sequence.
However, the insulating film containing Si and N has a high relative dielectric constant. Therefore, even if such an insulating film is made thinner and employed as the barrier insulating film, the dielectric constant of the overall interlayer insulating film is increased.
Also, the relative dielectric constant of the barrier insulating film containing Si and C is relatively low, i.e., about 5, as compared to a barrier insulating film containing Si and N. But such a barrier insulating film containing Si and C cannot sufficiently suppress leakage current.
It is an object of the present invention to lower the dielectric constant of an interlayer insulating film as a whole and to suppress change in the dielectric constant due to moisture absorption, while preventing corrosion of wiring and an increase in leakage current.
In the film forming method according to the present invention, the silicon-containing insulating film is formed by converting to a plasma a film forming gas selected from the group consisting of alkoxy compounds having Sixe2x80x94H bonds and siloxane compounds having Sixe2x80x94H bonds and an oxygen-containing gas selected from the group consisting of O2, N2O, NO2, CO, CO2, and H2O, and reacting the plasma components. It has been found that the resulting silicon-containing insulating film is dense, has high moisture resistance, has a low moisture content, and has a small relative dielectric constant.
Therefore, if the above silicon containing insulating film is employed as the barrier insulating films (a lower protection layer and an upper protection layer) that constitute the interlayer insulating film interposed between the upper wiring and the lower wiring, and sandwich the low dielectric constant insulating film, the dielectric constant of the overall interlayer insulating film can be lowered while preventing corrosion of the wiring and increase in the leakage current.
The semiconductor device of the present invention includes a silicon-containing insulating film whose peak infrared ray absorption intensity is in a range of wave number of 2270 to 2350 cmxe2x88x921, whose film density is in a range of 2.25 to 2.40 g/cm3, and whose relative dielectric constant is in a range of 3.3 to 4.3, formed on a substrate.
It has been experimentally found that the silicon-containing insulating film having such characteristics has high mechanical strength, is dense, is excellent in water resistance, and has a low amount of contained moisture, like the silicon nitride film, and has a relative dielectric constant smaller than that of a silicon nitride film.
In the manufacture of a semiconductor device, the above silicon-containing insulating film is formed to contact and cover the wiring or is formed as a protection layer on an insulating film that covers the wiring.
The silicon-containing insulating film of the present invention has a low dielectric constant, contains a low amount of moisture, is dense, and has excellent water resistance. Therefore, if a silicon-containing insulating film is employed as a protection layer covering the wiring, etc., corrosion of the wiring can be prevented by preventing moisture from entering the semiconductor device while reducing the parasitic capacitance between the wirings.
The upper and lower wirings and the interlayer insulating film interposed between the upper and lower wirings are provided on a substrate, and the interlayer insulating film is formed of the silicon-containing insulating film according to the present invention.
The interlayer insulating film includes, in order from the bottom, a lower protection layer formed of the silicon-containing insulating film according to the present invention, the main insulating film, and an upper protection layer formed of the silicon-containing insulating film according to the present invention.
If the main insulating film is a SiOF film, the silicon-containing insulating film according to the present invention can prevent the fluorine (F) from diffusing to the outer peripheral portions 5 of the silicon-containing insulating film. If the main insulating film is a porous insulating film having high hygroscopicity, the silicon-containing insulating film according to the present invention can prevent the ingress of moisture into the porous insulating film and thus prevent increase in the dielectric constant due to moisture absorption.
Also, since a silicon nitride film is not employed as the upper and lower protection layers for the main insulating film, and the silicon-containing insulating film having a low relative dielectric constant is employed instead, the dielectric constant of the overall interlayer insulating film can be reduced,